A perspective view, of a typical synchronizer ring for use in a speed variator is shown in FIG. 1. The inner surface 1 if the ring is subjected to intermittent surface contact with a rotating tapered cone under high pressure and the outer circumference of the ring is provided with key grooves 3 that are to come into engagement with keys. The outer edge of the ring circumference is provided with spaced chamfers 2 that mesh with chamfers on mating hub sleeve. In order for the synchronizer ring to exhibit its function, it must have high strength, high wear resistance and good compatibility with the mating members. Synchronizer rings have, therefore, been commonly fabricated of high strength brass which possesses these characteristics. "Pin" type synchronizer rings are also available that have a threaded portion on the outer circumference which comes into engagement with the mating tapered cone.
The demand for increasing the power output of speed variators is constantly growing and the prior art synchronizer rings made of high strength brass receive the high surface pressure exerted by either one of the mating members (i.e., tapered cone, keys, and chamfers on a hub sleeve). Because of the resulting decrease in the initial compatibility of the ring, it has frequently experienced one or more type of abnormal wear including bright surface wear and adhesive wear, and its useful life is inevitably shortened.
The present inventor has, therefore, conducted studies in order to develop a synchronizer ring for speed variators that is free from the aforementioned problems of the prior art version made of high-strength brass. As a result, the present inventor has found that this objective can be attained by the following synchronizer ring:
A synchronizer ring made of a Cu-base alloy that contains 20-40% Zn (all percents being on a weight basis), 2-8% al, and at least two components (intermetallic compound forming components) selected from among the following five elements, 0.1-3% of at least one of Ti, Zr and Cr, 0.1-3% Sn, 0.1-6% of at least one of Fe, Ni and Co., 0.1-5% Mn and 0.2-2% Si, and optionally at least one additional component that differs from said selected two components and which is selected from among 0-5% Mn, 0-3% Sn and 0-3% of at least one of Ti, Zr and Cr, and the balance being Cu and incidental impurities, said ring having either an oxide film layer of aluminum oxide (Al.sub.2 O.sub.3) base with an average thickness of 0.1-10 .mu.m or a work-hardened (e.g., shot-blasted or cold pressed) layer with an average thickness of 5-300 .mu.m formed in a selected area of the surface that is to have contact with at least one of the following mating members, a tapered cone, keys, or chamfers or a hub sleeve.
This synchronizer ring exhibits good initial compatibility with mating surfaces even under the high surface pressure exerted during high-output operations of a speed variator and as a result, only a minimum amount of abnormal wear will occur in the initial period of the use of the ring.
The present inventor has also filed copending application Ser. No. 97/157,634 directed to synchronizer rings for use in speed variators produced from copper base alloys.